// Circle class - circle element for scene - draws and manages a circle in the scene
Circle.prototype = new Shape();  
Circle.prototype.constructor=Circle;
function Circle(x, y, radius){
	this.center = {x:x,y:y};
	this.radius = radius;
	this.x = x-radius;
	this.y = y-radius;
	this.w= radius*2;
	this.h= radius*2;

	this.updateBoundary();
	this.draw = function(ctx){
		ctx.beginPath();		
		ctx.arc(this.center.x, this.center.y, this.radius, 0, 2 * Math.PI, false);		
		this.executeDraw(ctx);
	};
}
